Molding for manufacturing an inner conical recess for receiving an amputated extremity and process therefor

ABSTRACT

An inner conical recess fitting (1) which is connectable to the prosthesis and is intended for receiving a stump (17) of an amputated extremity can be fitted directly to the stump (17) without the aid of modeling in the following procedural steps: to mold the inner conical recess, a plastic which is shrinkable through the action of external influences, such as heat, is selected; a tube (14) which is made of this plastic and is open at at least one end and has a smaller diameter and a smaller length than the inner conical recess fitting (1) to be manufactured is extended and stretched, so that it has in every direction a greater dimension than the inner conical recess fitting (1) to be manufactured; and the widened and stretched molded piece (10) is placed on the stump (17) and is made to shrink through, e.g., application of heat at selected locations, until the fitting bears everywhere securely against the stump.

This application is a division of application Ser. No. 867,955, filedMay 29, 1986, (U.S. Pat. No. 4,783,293).

BACKGROUND OF THE INVENTION

The present invention relates to a process for manufacturing an innerconical recess or socket which is connectable to a prosthesis and isintended for receiving a stump (pedicle) of an amputated extremity. Theinvention also relates to a molded piece which is designed for use inthe process of the invention.

Inner conical recesses of this type, which directly receive ths stumpsof amputated extremities and therefore need to have been fittedextremely well to the shape of the specific stump, are manufactured in acompletely uniform manner, irrespsective of the material used in aspecific case. A negative impression is prepared of the stump, forexample, from plaster. This impression is filled with a suitable plasticto form the positive impression of the stump. The material of the innerconical recess is applied onto this positive impression, for example, bypouring on a suitable foam material or deep-drawing a thermoplasticsheet. This procedure is self-evidently very time-consuming andexpensive. With recent amputees there is in addition the problem thatthe stump is still undergoing changes which necessitate manufacture of anew shaft with a new inner conical recess a certain time after theamputation. Again the equipping of these patients (interim equipping) isrelatively time-consuming. The repeated modeling steps make itimpossible to manufacture the inner conical recess having the optimaldegree of accuracy.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved process for manufacturing inner conical recesses suitable forreceiving an amputated extremity.

A particular object of the invention resides in providing such a processwhich enables accurate manufacture of the inner conical recess in a lesstime-consuming way.

It is also an object of the invention to provide a molded part which issuitable for use in the process of the invention, as well as a kitincluding such a molded part and improved prostheses which aremanufactured according to the invention.

In accomplishing the foregoing objects, there has been providedaccording to one aspect of the invention a process for manufacturing aninner conical recess fitting which is attachable to a prosthesis forreceiving a stump of an amputated extremity, comprising the steps ofproviding a generally conically-shaped hollow molded part comprised of apolymer material which is selectively shrinkable in response toapplication of an external effect, this molded part being open at itsbase and being larger in size than the inner conical recess fitting tobe produced; placing the molded part directly on the stump of anamputated extremity; and applying to selected local portions of themolded part an external effect suitable to produce shrinkage of theplastic material, this effect being applied in an amount sufficient toproduce a degree of shrinkage so that the molded part conforms with theshape of the stump to produce the inner conical recess fitting.

In accordance with another aspect of the invention, there has beenprovided a molded part suitable for manufacturing an inner conicalrecess fitting which is attachable to a prosthesis for receiving a stumpof an amputated extremity, comprising a generally conically-shapedhollow molded part comprised of a polymer material which is selectivelyshrinkable in response to application of an external effect. The moldedpart is open at its base and has at its base and outwardly curled lipportion. The molded part has generally the shape of the stump which itis intended to receive and has a dimension in each direction, exceptaround the inner circumference of the lip portion, which is larger thanthe stump which it is intended to receive.

There is also provided according to the invention a kit formanufacturing a prosthesis portion adapted to receive a stump of anamputated extremity, comprising a hollow, generally cylindrical seatring which is open at both ends and is adapted to be fit around thestump of an amputated extremity, the seat ring having at one end anoutwardly curled lip portion; and a molded part as defined above,wherein the molded part is adapted to be inserted into the seat ringprior to fitting of the seat ring around the stump of an amputatedextremity and wherein the lip portion of the molded part is adapted tointerchange and be supported by the lip portion of the seat ring.

In addition, the invention has provided a prosthesis, comprising atleast one prosthesis member and, attached to the prosthesis member, aninner conical recess fitting for receiving the stump of an amputatedextremity, wherein the inner conical recess fitting is made according tothe process as defined above.

Further objects, features and advantages of the invention will becomeapparent from the detailed description of preferred embodiments whichfollows, when considered together with the attached figures of drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows an interim prosthesis having an inner conical recessmanufactured in accordance with the invention;

FIG. 2 shows a seat ring as an individual component;

FIG. 3 shows a molding according to the invention as an individualcomponent;

FIG. 4 schematically shows a blow mold for preparing a molding accordingto the invention; and

FIG. 5 schematically illustrates the fitting of the molded piece to thestump which is held in the seat ring, according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The process of the invention is characterized by the followingprocedural steps:

to mold the inner conical recess, a plastic which is shrinkable throughthe action of external influences is selected;

a tube which is made of this plastic and is open at at least one end andhas a smaller diameter and a smaller length than the inner conicalrecess to be manufactured is widened and stretched, so that it has inevery direction a greater dimension than the inner conical recess to bemanufactured;

the widened and stretched molding is placed on the stump and is made toshrink through local action of the suitable influences until the shafteverywhere bears against and conforms to the stump in the desiredmanner.

According to the invention, the inner conical recess is thus directlyprepared on the stump of the amputated extremity. As a result, it ispossible to dispense with the hitherto customary repeated modeling,which led to inaccuracies and required an appreciable amount of time.Fitting to the stump is effected by shrinking the previously expandedplastic part. With the customary shrinkable plastics, this shrinking canbe caused through local heat action, which is producible, for example,by hot air from a hair-dryer. This shrinkage is effected at temperatureswhich are comfortably acceptable to the human body. By means of thelocalized heating, it is possible to obtain a very accurate fit of theinner conical recess on the stump, indeed through cooperation of thepatient, in that the latter can indicate at any time when the desiredfit on the stump is obtained in the heated area.

To expand and stretch the plastic tube, it is particularly suitable touse a blow molding process in which the plastic is heated and expandedonto the contour of a blow mold by injection of compressed air.

The inner conical recess can thus be fitted to the stump in a simplemanner by using a premanufactured, correspondingly expanded molded piecewhich is made of a shrinkable plastic. Beginning with a tube which isopen at at least one end and has a smaller diameter than the innerconical recess to be manufactured (a "preform"), the molded piece isexpanded to a shape which has in every direction a greater internaldimension than the inner conical recess to be manufactured. With such amolded piece, final prostheses as well as interim prostheses can beprepared in a simple manner in orthopedic workshops by means of ahair-dryer.

In a particularly convenient manner it is possible to adapt the innerconical recess to the circumstances of the stump during wear of theprosthesis if the molding has at its open upper edge a curled rim withwhich it is securable in a premanufactured seat ring adapted to itsshape. This arrangement is particularly suitable for producing aninterim prosthesis. The seat ring is selected from a plurality of sizesfor the size of stump in question. The expanded molded piece is adaptedto the seat ring, so that the molded piece can be pushed onto the stumptogether with the seat ring. The seat ring can readily include atransitional attachment for the prosthesis, for example, one having aknee joint.

The invention will now be explained in more detail by reference to theillustrative embodiments depicted in the drawings.

FIG. 1 shows a leg prosthesis for a patient who has been amputated atthe thigh. To receive the thigh stump there is provided an inner conicalrecess 1 which, by means of an edge 2 at the upper open rim has beensuspended in a seat ring 3 of a type which is known. The seat ring 3 isconnected with a frame-like support 4 to a known modular prothesis 5which has a knee joint and an artificial foot 7, between which aprosthesis tube 8 extends.

FIG. 2 shows a view, from obliquely behind, of a seat ring 3 which has asomewhat oval shape and is adapted to hold in a ring-like manner a thighstump. The upper rim 9 has been widened outwardly and consrtucted to besoft. To form the inner conical recess 1, a molded piece 10 (FIG. 3)which is open at the top is suspended from above in the seat ring 3. Tothis end, the molded piece 10 has at the upper open edge a rim 11 whichis bent outwardly and matches the rim 9 of the seat ring 3.

FIG. 4 illustrates the production of the molded piece 10 in a blow mold12. The blow mold 12 has mold contour 13 whose dimensions in everydirection are greater than the dimensions of the ultimately requiredinner conical recess 1. A preform or blank 14, which is drawn in brokenlines in FIG. 4, is suspended in the blow mold. The blank has the shapeof an oversized test tube. In the blow mold the plastic material of theblank 14 is heated up, and the interior is subjected to compressed air.As a result the blank takes on the contour 13 of the blow mold, so thatthe molded piece 10 of FIG. 3 results. It is removable after separatingthe two mold halves 15, 16.

FIG. 5 illustrates that the molded piece 10 is suspended in the seatring 3 and that this arrangement is pushed over a stump 17 of theamputated extremity. The expanded molded piece 10 has at every locationlarger dimensions than the stump 17 or the inner conical recess 1 to beproduced, so that the stump is in contact with the molded piece 10 onlyin the upper part of the seat ring 3. Since the size of the seat ring 3has been selected for the stump 17 in question and the molded piece 10has been matched to the shape of the seat ring 3, a ring-like fit of themolded piece 10 on the stump 17 is present in the upper region. Theremaining fit is then effected through the action of hot air from ahair-dryer 18 on the molded piece 10, as a result of which the lattershrinks in the area of the local heating. By this process the moldedpiece 10 can be gradually fitted to the shape of the stump 17, theresult being the inner conical recess 1 which precisely fits the stump17.

FIG. 5 additionally shows a circular opening 19 in the molded piece,which serves for passing through the lower end of a tricot stockingwhich is drawn over the stump 17, so that the plastic of the moldedpiece 10 does not stick to the skin of the stump 17.

From previous experience it has been found that only a relatively smallnumber of different size seat rings 3 is required to accommodate thevarious possible sizes of stumps 17. Accordingly only a correspondingnumber of premanufactured molded pieces 10 is required in order to beable to manufacture the requisite inner conical recess 1 for all stumps17. Once the inner conical recess l has been produced, there is nodifficulty in producing a complete prosthesis shaft by applying furtherplastic coats. In this way it is also possible to provide suitablefastening means for the remaining prosthesis elements.

What is claimed is:
 1. A molded part suitable for manufacturing an innerconical recess fitting which is attachable to a prosthesis for receivinga stump of an amputated extremity, comprising:a generallyconically-shaped hollow molded part comprised of a polymer materialwhich is selectively heat-shrinkable in response to application of anexternal effect, said molded part being open at its base and having atits base an outwardly curled lip portion, and said molded part havinggenerally the shape of the stump which it is intended to receive andhaving a dimension in each direction except around the innercircumference of the lip portion which is larger than the stump which itis intended to receive.
 2. A molded part as claimed in claim 1, whereinthe molded part includes an aperture in a portion thereof generallyopposite to said base.
 3. A kit for manufacturing a prosthesis portionadapted to receive a stump an amputated extremity, comprising:a hollow,generally cylindrical seat ring which is open at both ends and isadapted to be fit around the stump of an amputated extremity, said seatring having at one end an outwardly curled lip portion; and a generallyconically-shaped hollow molded part comprised of a polymer materialwhich is selectively shrinkable in response to application of anexternal effect, said molded part being open at its base and having atits base an outwardly curled lip portion, and said molded part havinggenerally the shape of the stump which it is intended to receive andhaving a dimension in each direction except around the innercircumference of the lip portion which is larger than the stump which itis intended to receive, wherein the molded part is adapted to beinserted into said seat ring prior to fitting of the seat ring aroundthe stump of an amputated extremity and wherein the lip portion of themolded part is adapted to interengage and be supported by the lipportion of the seat ring.